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A thoroughly sporadic column from astronomer Mike Brown on space and science, planets and dwarf planets, the sun, the moon, the stars, and the joys and frustrations of search, discovery, and life. With a family in tow. Or towing. Or perhaps in mutual orbit.

Almost ten years ago I got to be involved in an astronomical experiment. The US Air Force had recently completed a technologically sophisticated telescope on Haleakela, the highest peak on Maui, for the purpose of spying on satellites as they went overhead. The National Science Foundation was interested to know if the new telescope might prove useful for astronomers, too, so they recruited a few test cases to come see if they could make it work.

The tests were, ultimately, ambiguous. We were trying to observe Saturn’s moon Titan to see if we could take images of hurricane-sized storms moving across its surface. We were stymied as much by horrendously bad weather (on Haleakala, not on Titan), as we were by cultural differences between astronomers and the Air Force. (My favorite: our observations of Titan were temporarily classified, because “Titan” is the same word as “titan” which is a missle. The people doing the classifying thoroughly understood that we were observing the moon of Saturn but, by the rules, any observations of “[T]itan” were to be classified.)

But though we were generally stymied, one moment at that telescope will stick in my memory forever. We were waiting for Titan (the moon of Saturn) to rise high enough in the sky that night and watching over the operators’ shoulders as they spied on satellites. Whenever they were foreign satellites we were kicked out of the room. But whenever they were U.S. satellite we could stay and watch.

At 4am the night before, as we were driving down the mountain after a night of observing, we had listened intently to the news of the Space Shuttle parked at the International Space Station and the installations to be done that day. They were having problems, apparently, with getting a solar panel to unfurl correctly. We went to sleep not knowing what had happened. As we drove back up the mountain the next day we had still not heard any news.

Around 8pm, though, Elvis, one of the operators, said “ISS coming!” meaning that the International Space Station was soon to fly overhead.

“Hey, you guys seen the ISS before?” Elvis asked.

“Not that I know of” I said.

“This a sight to see; hold on.”

And the giant telescope swung to the horizon and started tracking the space station as it went across the sky and the other operator came in and starting making adjustment on the computer and then, suddenly, the Space Station came into focus.

It looked much like all of the other pictures of the Space Station that I had ever seen before with two exceptions. First, the solar panels were unfurled.

“Ah ha!” we said. “I guess they were successful last night.”

Second, we could see the Space Shuttle parked next to it. Every other picture I had ever seen had been taken from the Space Shuttle, so I had never seen what it looks like when the shuttle is parked right there.

The view was so good that if a spacewalk had been happening right then and an astronaut had turned around to wave at the earth we would have seen him well enough to know to wave back.

The telescope tracked the Space Station for about 4 minutes. When it was over, I picked my jaw up off the floor. It was, perhaps, the most amazing pictures I had ever seen a telescope make before, and it was just over our heads, rather than in the remote depths of space.

Only a few weeks ago, on these very pages, I tried to remind people to Look Up! To remember that stars and planets and galaxies are not abstract things that we read about but are real concrete and viewable things in the sky above. But, really, for most of my life, I’ve been just as guilty when it comes to those other things that occupy our night skies: the satellites. It’s not that I don’t see them all the time when I am looking at the sky, but I never think of them as anything more than spots of light moving across the heavens. Sure, I know all about the Space Station. I use the Hubble Space Telescope as often as I can. I think about the astronauts and the Space Shuttle and watch NASA TV to make sure the launch and the walks go ok. But somehow I still fail to make that cognitive leap that reminds me that these things are real, and are really in the skies over head.

Until this week.

Knowing that the Shuttle was up visiting the Hubble Space Telescope for the last time, I got an overwhelming urge to see them both, to somehow make a visual connection with the astronauts who are up there risking their lives so that people like me can continue to make astronomical discoveries. I knew that, in theory, you should be able to see such things, but I didn’t really know how. I did what any rational person would do in 2009, which is to search Google. And I found my new obsession: www.heavens-above.com

Simply tell the web site your latitude and longitude and it will tell you all of the bright satellites that will go overhead tonight.

I tried it the other night. The Space Station was making what I now realize was a particularly favorable pass. At 9:51pm I went outside (a full 2 minutes early, just in case, though I need not have). I waited. I traced precisely where I thought it was supposed to go and stared and stared just in case it was a bit faint to see in the glow of the Los Angeles skies. And then, precisely, on schedule, it silently and majestically moved from the southwest horizon to nearly overhead to the northern horizon over the course of about 4 minutes. It was brighter than anything else in the sky at the time.

I had seen it before, I am certain. But I had never seen it and known what I was seeing. I ran back inside and said to my wife Diane:

“I just saw the Space Station go overhead. It was one of the most amazing sights in the sky I have ever seen!”

She looked at me, nodded, and went back to the email she was writing.

OK. I get it. Satellites aren’t for everyone. But they’re out there. They’re real. They’re waiting. That bright light travelling across the sky contained three people who at that precise moment could have been looking down and seeing the crescent earth with the sun still illuminating the Pacific while California was now bathed in dark. Those people are really there.

As for the Space Shuttle, which set me on this mission, it hasn’t been visible yet. You can only see satellites when – like an airplane high in the sky at sunset – they are still illuminated by the sun while you are in the dark. By chance that has not happened over California yet while the Shuttle has been up. I might get a chance on Friday, when it is low in the sky around 5am. I will definitely wake up for it. It’ll be my last chance to see the Hubble Space Telescope and the Shuttle together and to remind myself that up there these things that we built, these people that fly to them, are all real, and finally on their way back home.

We astronomers like to toy with the ideas of life and of death. We name distant objects after gods of the dead and underworld, like Orcus or Pluto, we eagerly discuss cannibalistic galaxies and gamma ray bursts that would wipe out civilizations for light years in radius. We talk about catastrophic impacts and the possible slow death of the entire universe. But, usually, it is just a vicarious show. Nothing that we study out there in the universe will is likely to actually affect anything down here on earth. Nothing that we do is really a matter of life and death.

Except for this week.

This week, for the sake of astronomy, seven people will strap themselves on to the top of a controlled explosion and launch themselves almost 200,000 stories into the air. If all goes well, they’ll spend nearly two weeks confined to a tiny container holding the only patch of livable space for 400 miles in any direction, before they drop back to earth in a flaming descent that transforms into a supersonic glissade to the ground.

The seven are the astronauts on the final Space Shuttle servicing mission to the Hubble Space Telescope. If they are able to carry out everything on their extensive list, they will leave behind an enormously capable telescope capable of years more of distinguished and fascinating scientific inquiry.

Astronomers the world over will rejoice, but I will rejoice a bit more than average. A year ago, I proposed to the committee in charge of the Hubble Space Telescope that they allow me to spend a significant amount of time on the telescope to use one of the brand-new instruments being put in by the astronomers to study the origin of the Kuiper belt. It was a bit of a long shot, I thought. These committees tend to favor things such as figuring out the origins of distant things, like galaxies, or the universe itself. Our local neighborhood is often overlooked. But the committee liked the idea and now all that stands between me and getting to use this fantastic new instrument in space is the fact that the instrument itself is currently sitting in Florida. At least as of this moment. But come blast-off it and the seven astronauts will be on their way to space.

This moment almost never happened. If I were in charge, it never would.

After the 2003 Space Shuttle Columbia break up over Texas, NASA declared that the only safe way to fly the Space Shuttle was to go to the Space Station where it could be inspected and, if problems were found, astronauts could temporarily stay while repairs or rescues were mounted. But because of their very different orbits, you can’t get to the Space Station if you go to the Space Telescope. Thus, there would be no more flights to the Space Telescope and it would soon plummet to the earth and burn up in the atmosphere.

There was a great outcry. Hubble is invaluable! Hubble is a national treasure! It seemed as if every astronomer out there had stories to tell about why Hubble was spectacular.

I agreed. I had my own stories, even. Many of the fabulous finds about dwarf planets over the past decade have been made by or aided by the Hubble Space Telescope. And there are many many more things that I still want to do with it. And then I said that it was OK to let it die. Hubble had had a spectacular decade and a half, and if it was not safe to refurbish it anymore we astronomers needed to celebrate its legacy, mourn its loss, but accept that it was for the best. This was no longer an abstract matter of galactic life and cosmic death: this was a matter of real life and, quite possibly, death. This actually mattered.

I grew up in Huntsville, Alabama, a thoroughly dedicated space town, and reminders that things do not always go as planned are strewn throughout the city. The high school to which I went was named after Gus Grissom, who died during a pre-launch test of the Apollo 1 mission. Ed White and Roger Chaffee – who died along side Grissom – have their own schools just across town. You can see the Challenger school from the back deck of my parent’s house.

I love space exploration. I love human space exploration. I grew up on it. I wanted to be part of it. I became an astronomer because of it. I understand – I think – the risks, and am even willing to accept them. Sometimes. But not blindly. I feel that many of the astronomers pushing and pushing and pushing to get the Shuttle to fly to the Space Telescope never once thought about the risks, never drove around a town with schools memorializing astronauts who never came home. This actually mattered.

What are the risks of catastrophic failure, as the worst-case scenario is known? I have heard absurdly precise estimates of 1 chance in 187, though I neither know how these numbers are arrived at nor put much faith in them. I do know that this next mission is designated STS-125 – the 125th Shuttle flight. Two have ended in disaster. That’s 1 in 64. While that’s not quite Russian roulette with a six-shooter and a single bullet, neither is it a short drive to the office in light traffic. It was worth thinking hard about this. This actually mattered.

In the end, the tea leaves were clear from the beginning. The outcry was too loud for the Hubble to be allowed to fall from the sky. The Space Shuttle would go after all.

It’s probably good that I wasn’t in charge. I don’t think I ever want to be in the position of making decisions that could directly lead to someone never coming home to their family again. But someone has to make those decisions. I would have chosen differently, but I understand the choice. The astronauts themselves know what they are getting in to and are itching to go. Who am I to say no? And, since the decision is made and they are indeed going, I’ll be the one watching from down here on earth cheering loudly, remembering the excitement I’ve felt with every blast off I remember from Apollo on. And this time I’ll be cheering even more loudly, thinking about the years of discovery ahead and the origins of the Kuiper belt and things about which I have not even begun to dream.

You will likely not be surprised to learn that I am a non-religious person. I draw my spiritual inspirations from Etruscans and Inuits and small children and the full moon itself. And yet, when searching for the right incantation, the right words of encouragement and amulet against harm, the best one that comes to mind describes something that those seven astronauts will both have in an almost literal sense and certainly need in the intended sense:

[I've been watching the moon, which made me remember a much earlier column that almost no one read. Forgive the rerun, but watch the moon!]

If your skies have been clear for the past week you might have been noticing -- as I have been -- the slow but unstoppable growing of the moon. There's nothing new here. It does essentially the same thing every 28 days, but it is still a show worth watching.

In my backyard I see this: each night as the moon moves further and further in its circle around the earth and we see more and more of the illuminated half, the moon is getting just a little brighter. In a few days, as the moon finally goes from just-barely-not-full to finally-completely-full, the moon will finally brighten its last incremental amount and it will be its brightest of the month, though only a little brighter than it was the night before.

This gentle brightening to a muted peak sounds prosaic and reasonable. But it is not true.

I remember once being out on a backpacking trip in the wild mountains inward of the Pacific coast south of Monterey. Some friends and I had hiked all day to make it over a range and down to the bottom of a creek where a little stream of hot water poured out of the earth making a tiny pool in which to soak sore legs and shoulders. We camped a bit away from the hot pool, ate a warm dinner as the sun was going down, and finally began climbing our way to the top of the little ridge separating us from the hot spring. We didn't even bother with flashlights in the dark because the full moon had made the entire woods faintly glow -- plenty of light to get around at night even in the dark of the wilderness. As we had almost reached the top, though, somebody silently flipped a switch and a blinding spotlight was suddenly tracking us from the ridge.

This was miles away from any roads or machinery down a long windy trail, so perhaps I could have reasoned my way out of the situation given a little time for relaxation, but, in the instant, I did what I think most anyone would do when unexpectedly illuminated by a spotlight deep in the woods far from where anyone or anything should be: I yelped. Loudly.

My yelping didn't affect the spotlight, which refused to flinch. It refused to flinch, I realized an embarrassed moment later, because it was no spotlight, it was the moon. It had been hiding behind the ridge until we had gotten near the top, and as we rose over one bump it suddenly revealed itself like the flip of a switch. My credibility as a young astronomer (I had just started graduate school that year) was seriously diminished amongst the friends who had seen me frightened of the moon.

Which is to say that the full moon is really bright.

The fact that the full moon is bright is perhaps not a startling fact, but what is startling is that if I had been coming over the ridge on my way to the hot pool and I had seen the moon a day earlier or a day later, I would never have mistaken it for a spotlight.

You don't have to take my over-tired-from-hiking-all-day's impressions for it. If your skies are clear this week as the moon is finally puffing towards full, go outside and see for yourself. Go out on Wednesday, two days before the full moon, and look around. Check out the barely visible shadows. See what fuzzy shapes you can make out in the distance. Look up and notice that the moon is definitely not fully illuminated, but it is getting close.

Go out Thursday. To really do the job right you should go out an hour later than you did the night before, since the moon will have risen an hour later. Look around. You probably won't be able to tell any difference at all from the night before. Same vague shadows, same fuzzy details. And then look at the moon. Definitely bigger, but one edge is still a little flattened. Tomorrow it will indeed be full.

Finally, go out on Friday, an hour later still if you can. Stare right at the moon, if your eyes can stand it. It does look like a spotlight up there in the sky. It is much brighter than it was just the day before. Look at the now-crisp shadows on the ground and the sharp details on the rocks and the plants that you can now pick out. Now go ahead, if you need to, and let out a little bit of a yelp. I'll be understanding.

What is going on with the moon? How can it get so much brighter in just a day? Who turned on the spotlight?

In medieval paintings, saints and anyone else holy are always depicted with a halo around their heads. Unlike modern halo depictions, which look like a gold ring hovering slightly above the hat line, these medieval halos appear more like a general glow coming from behind the entire head. Whenever I see one of these glowing medieval halos I think about how bright the full moon is.

I have a hypothesis -- totally without the benefit of supporting research, necessary expertise, or, likely, even minor merit -- that the medieval painters painted halos like this because they had seen such halos around their own heads. And I know what the painters saw, because I have a halo around my head, as well.

Here's another experiment to try. Go outside on a bright sunny day and start watching your shadow. Walk along until you find a place where the shadow of your head is falling on grass. Focus on your head shadow while you continue to walk, letting the background grass blur in you vision. You will gradually notice that there is a diffuse glow around the shadow of your head. It won't be around any other part of your body, and you won't see the slightest hint around anyone else's head. Point out your halo to any else and they will see precisely the same thing: a halo around their own heads and nothing around yours. Everyone is holy to themselves.

In reality what you are seeing is not some sort of corporeal representation of your own ego or a mystical aura of self-realization, but simply a literal trick of lights and shadows. When you are looking at the shadow of your own head, you are looking, by necessity, directly in the opposite direction of the sun. Stop focusing on your glowing halo for a minute and now focus on the grass itself. You'll notice that in the region where your halo is you will not see a single dark spot due to a shadow of one blade of grass on another. There can't be any shadows; with the sun directly behind you, any piece of grass that you can see can see the sun, so it can't be in shadow. Start looking away from your head shadow and you notice that you are now starting to see collections of tiny shadows, so the overall scene gets darker and darker even though it, too, is fully illuminated by the sun. Your halo is simply the total lack of shadows that can only occur when you are looking almost exactly opposite the sun. I've seen my halo from many places, on many surfaces: on grass or rough dirt or asphalt while walking, even on the tops of a forest full of trees while looking out of the window of an airplane flying low enough right before landing that I could pick out the shadow of the fuselage and see a beautiful glowing ring around. Anywhere you have sunlight and a surface rough enough to make millions of tiny shadows you get to glow the glow of the saints.

And so it is with the moon. When you look at the full moon you are almost looking at where the shadow of you head would be. The sun, though it has set over the horizon, is directly behind you as you face the full moon. If you could see down to the surface of the moon, you wouldn't see a shadow anywhere, not in the craters, not amongst the craggy mountains, but, more importantly not even at the finest scales of the rocky dust that covers most of the surface. The next day, when the moon is just past full, the shadows will begin to reappear and the spotlight will be extinguished.

It happens every month. It's just a trick of light and shadows. But, every now and then, I still look up at the full moon and think about saints and I feel a little bit of a yelp deep inside.